This invention relates to internal-combustion engines and to hot-gas engines. In particular the present invention is a series of different compound internal-combustion hot-gas engines. Each compound engine is housed in a single engine casting wherein an internal-combustion means and a hot-gas means are mechanically and dynamically connected by use of a single crankshaft. The internal-combustion means possesses one or more cylindrical combustion chambers which are made expansible by use of a reciprocating piston therein. The internal-combustion means operates in either the two-stroke or four-stroke cycle, thereby burning a fuel-air mixture and then expelling hot exhaust gases. A recuperator, usable to both said means, receives the hot exhaust gases and transfers thermal energy therefrom, and thereby thermally drives the hot-gas means. The hot-gas means possesses two or more cylindrical chambers which are made expansible by single-acting or double-acting reciprocating pistons therein. The hot-gas means operates by expansion and/or contraction of a constant mass of motivating gaseous medium, which is heated or cooled in one of the plurality of continually communicating expansible cylindrical chambers with the medium regeneratively transferable therebetween. A liquid coolant usable to both said means convectively transfers waste thermal energy from said means to a radiator which thermally communicates with the ambient environment. The cylindrical axes of said expansible cylindrical chambers within the compound engines are geometrically distributed side-by-side and parallel either: (1) in a single plane (linear engine); or (2) in two planes forming a vee with the axes all intersecting the line common to the two planes, and where the vee angle is .pi./3 radians, .pi./2 radians, or arbitrarily variable from 0 to .pi. radians. Although the invention is particularly useful as a prime mover for automobiles, trucks, busses, locomotives, maritime vessels, farm implements, and stationary power sources, it is not limited to such uses.
While the preferred embodiments disclosed herein typically employ hot-gas means, such as closed Stirling-cycle units, other hot-gas means may be used subjecy to the performance characteristics of such other hot-gas means. Also, while the preferred embodiments disclosed herein typically employ internal-combustion means, such as four-stroke-cycle spark-ignition or compression-ignition units, or such as two-stroke-cycle spark-ignition or compression-ignition units, other internal-combustion means may be used subject to the performance characteristics of such other internal-combustion means. Additionally, while the preferred embodiments disclosed herein are compound engines wherein expansible cylindrical chambers are distributed as described above, other geometrical distributions of expansible cylindrical chambers may be used subject to the performance characteristics of such other compound engines. Throughout the remainder of this patent application the term "cylinder" shall mean "a cylindrical chamber with a reciprocating piston therein thus making said chamber expansible".
There has been momentous activity and significant progress in the development of prior art internal-combustion engines. For example, reference is made to the host of U.S. patents in class 123. Today internal-combustion engines are produced in mass and are commercially available in a multitude of variations. The variations range nearly continuously from small single cylinder engines providing output power of a fraction of a kilowatt to very large engines providing megawatts of output power. There are, however, only two practical mechanical types of internal-combustion engines. They are (a) the rotary engine, and (b) the crankshaft engine with reciprocating pistons. The crankshaft engines have pistons operating in cylinders which are arranged in linear, vee, flat-planar, or radial geometrical distributions about the axis of the crankshaft. The crankshaft engines typically operate in either the four-stroke cycle or in the two-stroke cycle. Reference 1 provides a review of internal-combustion engines.
During the past thirty-five years there was an increase in activity and progress in the development of practical hot-gas engines. For example see all the U.S. patents in class 60/24, and as of Jan. 1976 those in class 60, subclasses 517-531. We have reviewed abstracts for all these patents at the Linda Hall Library, Kansas City, Mo. However, after corresponding with several companies that own patents or licensing agreements relating to hot-gas engines, we found hot-gas engines are now commercially available only as laboratory or lecture demonstration devices which deliver a fraction of a kilowatt of output power. Practical hot-gas engines having output power from 5 to 300 kilowatts remain, to this day, to be experimental devices which are available only through intricate licensing agreements with owners of prior art patents. There are three different basic mechanical types of the larger hot-gas engines. They are: (a) the rhombic-drive displacer-piston engine, (b) the swashplate engine with reciprocating pistons, and (c) the crankshaft engine with reciprocative pistons, all of which are described in Reference 2 and in several U.S. patents in class 60, subclasses 24 and 517-531.
We discovered through the use of classical Lagrangian mechanics that the dynamical motion of all basic moving parts of any prior art internalcombustion engine and any prior art hot-gas engine, except for free-piston hot-gas engines, can be analytically described by mathematical functions of .alpha. the angular position, .alpha.' the angular velocity, and .alpha." the angular acceleration of the engine's output shaft or crankshaft. From the veiwpoint of classical Lagrangian mechanics these two classes of engines are each mechanical systems with only one degree of freedom, i.e., .alpha. the angular position of the crankshaft. We deduced in that manner that internalcombustion engines and hot-gas engines are compatible mechanical systems.
We also noted the following four thermodynamic features of these two classes of engines:
1. that prior art internal-combustion engines burn a fuel-air-mixture, do work (Joules), and then release hot exhaust gases to the ambient environment; PA1 2. that prior art hot-gas engines do work by utilizing an external combustion unit which also releases hot exhaust gases to the ambient environment; PA1 3. that both of these classes of prior art engines utilize an air- or liquid-coolant system; and PA1 4. that the net thermodynamic hot-gas cycle and the Otto cycle for internal-combustion engines bear significant similarity. We deduced from these four points that internal-combustion engines and hot-gas engines are also thermodynamically compatible, although the basic thermodynamic principles of their cycles are different.
In prior art approaches, internal-combustion engines and hot-gas engines have been developed as separate means. The fuel conversion efficiency of practical prior art internal-combustion engines is rated from about 15 to 28 percent, and for prior art hot-gas engines is theoretically rated from about 28 to 38 percent. Internal-combustion engines lose thermal energy to the ambient environment by three processes: (a) radiation, (b) convection through the coolant, and (c) in the exhaust gases. For example, thermal energy from the exhaust gases of present automobile engines provide sufficiently high temperatures in catalytic converters to cause chemical reduction of noxious gases. Hot-gas engines possess external combustion chambers which also expel exhaust gases that cool by expanding to ambient pressure, thus doing useless work on the ambient atmosphere. Hot-gas engines also lose thermal energy to the ambient environment through radiation and through convection of the coolant. Prior art internal-combustion engines and prior art hot-gas engines both operate at efficiencies well below the maximum obtainable efficiency of an ideal Carnot engine operating between the same two absolute temperatures. The application of the present invention in achieving further thermal compatibility and thereby efficient fuel conversion is to provide compound engines wherein an internalcombustion means is the combustion unit for a hot-gas means. In our compound engines thermal energy is recuperated from the exhaust gases of the internal-combustion means and transferred by conduction or by heat pipes to the heater of the hot-gas means. The opening and closing of the exhaust and intake ports in the cylinders of the internal-combustion means can be cyclically timed to facilitate thermal and output torque balance between the internal-combustion means and hot-gas means of the compound engine.